Video disc players have inherent advantages in playing back video programs as compared with video tape players, e.g., the ability to quickly access the recorded information, relatively low replication costs, relatively simple mechanical requirements, etc. This, unfortunately, is accompanied by a basic disadvantage relating to tracking errors. Specifically, a forward or backward skip of one track on a helical scan VTR results in only a one field error in the location of the pick-up transducer. A single skip of one track convolution in a presently available video disc player (e.g., the RCA model SFT-100) results in an eight field error in the recovered signal. In another known player a skip of one track results in a two field error for disks recorded at a constant angular velocity.
It is known that one may correct tracking errors in a video disc player on a field-by-field basis thereby placing video disc players on a par with video tape players. As an example, in U.S. Pat. No. 4,313,134 of Rustman et al., a video disc system is disclosed wherein field numbers are recorded in pulse code modulation (PCM) form during the vertical interval of each video field. This has become known as a digital auxiliary information code (hereinafter DAXI code). Tracking errors (e.g., locked or skipped grooves or information tracks) are detected in a player by noting an improper sequence of two or more decoded DAXI field numbers. Correction of the error is provided by means of a transducer deflector (e.g., a stylus "kicker" solenoid or piezoelectric element) which radially translates the pick-up transducer in a direction to reduce the tracking error until such time as the field numbers again form an orderly sequence. Other patents relating to the DAXI code, its generation, recovery and use in video disc player include U.S. Pat. No. 4,308,557 of C. B. Dieterich, U.S. Pat. No. 4,307,418 of Mindel et al. and U.S. Pat. No. 4,309,721 of Christopher.